Molded case circuit breaker

ABSTRACT

A molded case circuit breaker comprising a contact arm movable between circuit closed and open positions, a collapsible mechanism including a releasable member having one end normally engaged with a latch member of an automatic trip unit, a pair of toggle links provided between the movable contact arm and the releasable member, and a tension spring stretched between a manually operable handle and a toggle knee of the toggle links, the other end of the releasable member having a wedge member swingably mounted thereto. When an automatic trip occurs, the wedge member slidably enters between one of the toggle links and a stationary pin secured to the molded case to prevent the contact arm from rebounding toward its circuit closed position.

United States Patent 11 1 Tazuki 1111 3,805,199 [451 Apr. 1-6, 1974 IMOLDED CASE CIRCUIT BREAKER Satoru Tazuki, Takamatsu, Japan Inventor:

Tokyo Shibaura Electric Company, Ltd., Kanagawa-ken, Japan Filed: Oct.30, 1972 Appl. No.: 302,297

Int. Cl. H01h 3/46 Field of Search 335/191; 200/153 G References CitedUNITED STATES PATENTS 3.62Ll89 11/1971 Link ct al. 200/153 0 PrimaryExaminer-Harold Broome I Attorney, Agent, or Firm Oblon, Fisher, Spivak,McClelland & Maier 57] ABSTRACT A molded case circuit breakercomprising-a contact arm movable between circuit closed and openpositions, a collapsible mechanism including a releasable member havingone end normally engaged with a latch member of an automatic trip unit,a 'pair of toggle links provided between the movable contact arm and thereleasable member, and a tension spring stretched between a manuallyoperable handle'and a toggle knee of the toggle links, the other end ofthe releasable member having a wedge member swingably mounted thereto.When an automatic trip occurs, the wedge member slidably enters betweenone of the toggle links and a stationary pin secured to the molded caseto prevent the contact arm from rebounding toward its circuit closedposition.

3 Claims, Drawing Figures PATENTEH APR 1 6 I974 SHEET 1 [IF 2 H wtMOLDED CASE CIRCUIT BREAKER BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates generally to molded case circuitbreakers of the type including a springbiased releasable memberreleasably held by an automatic trip unit in a position to maintain amovable contact in its closed position. More particularly, the inventionrelates to such circuit breakers as characterized herein including meansfor preventing rebound of the movable contact member toward its closedposition following release of the releasable member.

2. Description of the Prior Art An example of amolded case circuitbreaker of the character described herein is disclosed in US. Pat. No.3,134,879 of George E. Gauthier et al., assigned to General ElectricCompany.

The prevention of rebound of the movable contact,

arm toward the circuit closed position upon the occurence of automaticrelease due to an overloaded condition is required in order tosufficiently maintain the leasable member to engage with a movablecontact arm upon the occurence of an automatic tripping operinterruptiondistance of the movable contact arm from its circuit closed position.

Although molded case circuit breakers as heretofore known have beensuccessfully used, some problems remain which prevent them from beingentirely satisfactory. In accordance with the circuit breaker disclosedin US. Pat. No. 3,134,879, for example, two components, namely thehook-like extension of the releasable member for engaging a slot in themovable contact arm and the swingable member supported in the moldedcasing so that its front edge engages one of a pair of toggle links,were required; As a result, the circuit breaker is expensive tomanufacture and it also is complicated to assemble.

In addition, in electric circuit breakers of substantial capacity, suchas 2000 amperes, relatively heavy parts and heavy operating springs arerequired to maintain the necessary contactpr'essure. Accordingly, asubstantially large shock is repeatedly imposed on the toggle link bythe thin front edge of the swingable member every time that automaticrelease occurs. As a result, mechanical fatigue of the toggle linkage,the toggle kneeand the pins for pivotally supporting the link endsfrequently occurs so that the circuit breaker cannot achieve theperformance initially intended.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention contact arm from rebounding toward its initial closed positionupon being operatively moved toits open circuit position. I

Another object of the present invention is to provide a new, improvedand unique molded case circuit breaker of the character described havingimproved resistance to mechanical fatigue of the collapsible mechanismthereof, including the toggle linkage and the pivotally supporting pinsthereof. 1

In accordance with one aspect of the invention, the foregoing objectsand others are attained through the provision of a molded case circuitbreaker which comprises a molded case formed of a suitable insulatingmaterial, at least one movable 'arm mounted in the molded case so as tobe capable of movement between closed and open circuit positions, anautomatic trip unit having a latch member capable of movement to areleasable position in response to an overloaded circuit condition, areleasable member pivotally supported in the molded case and having oneend thereof normally engaged by the latch member, a pair of toggle linkspivotally engaged with each other at their one ends, with the other endsof the toggle links being pivotally engaged, respectively, to thereleasable member and the movable contact arm, a manually operablehandle pivotally supported in the molded case and movable between thecircuit closed and open positions, a tension spring stretched betweenthe manually operable handle and the interconnecting knee point of thetoggle links, a stationary guide member mounted in the molded case, anda wedge member swingably mounted on the to provide a new, improved andunique open and clos- 'ing mechanism for use in a molded case circuitbreaker having minimum parts for preventing a movable releasable member,the wedge member being capable of sliding between one of the togglelinksand the stationary guide member when the releasable member isautomatically tripped by the latch member. whike the manually operablehandle is positioned in the circuit closed position.

I BRIEF DESCRIPTION OF THE DRAWINGS nection with theaccompanyingdrawings, wherein like reference numerals designate like orcorresponding parts throughout the several views, and in which:

FIG. 1 is an elevational view, in section, of one embodiment of a moldedcase circuit breaker constructed in accordance'with the presentinvention;

FIG. 2 is a partial view of FIG. 1 showing'the manu-' ally operablehandle in its open position; and

FIG. 3 is a partial view of a molded case circuit breaker with thehandle shown in a circuit open position having resulted from anoperation of the automatic trip unit.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT the casing and a loadterminal conductor 12 mounted on the same. The line terminal conductor11 has a sta tionary main contact l3'at one end thereof and an auxiliarystationary arcing contact 14 at an intermediate portion thereof in itslengthwise direction.

A trip unit 15 having a latch member 16 which includes a conventionalthermally actuated trip unit and an electromagnetic operated tripmechanism, is mounted in the casing at a leftward portion thereof, asseen in the Figure, and the line terminal conductor 12 is introducedinto the trip unit for exciting a magnetic pole unit of theelectromagnetic trip mechanism and for heating a bi-metallic unit of thethermally actuated trip unit, as is well known. The line conductor 12 isfinally connected to a conductor 18 also mounted on the base 17. I

A movable contact arm 19 is pivotally mounted in the casing 10 forsupporting a movable main contact 20 for engaging with and separatingfrom the main stationary contact 13 to carry out the making and breakingoperations of an electric circuit and a movable arcing contact 21 forengaging with and separating from the auxiliary stationary contact 14.

For convenience of illustration, only one movable contact arm 19 and itsassociated parts and a single arrangement of stationary contacts 13 and14'supported on the load terminal conductor 11 have been shown but it isto be understood that generally there are other movable contact arms andload terminal conductors arranged perpendicularly to the surface ofillustration in parallel fashion to thereby provide a poliphase ormulti-pole type circuit breaker. In order to simultaneously carry outmake and break movement of the aforementioned movable contact arms 19,an operating rod 210 is provided at one end thereof extending over theparallel movable contact arms 19.

A manually operable handle 22 is provided, having an upper end thereofextending through a slidable top cover 220 arc-tightly sealing thecasing 10 and a lower end pivotally mounted on a pin 23 secured in thecasing 10. A releasable member 24 having one end normally engageablewith the latch member 16 of the trip unit 15 is also provided. A pair oftoggle links 25 and 26 are rotatably pivoted to each other at respectiveends thereof by a pin 27 which acts as a toggle knee. The toggle link 25has its other end rotatably pivoted to the releasable member 24, and thetoggle line 26 has its other endrotatably pivoted to the movable contactarm 19.

. A tension type spring 28 is stretched between the handle 22 and thetoggle knee 27, and thus when the spring 28 is positioned as shown bythe manual operation of the handle 22, the toggle links 25 and 26 arestraightened so as to engage the contact 20 of the movable contact arm19 with the stationary contact 13 of the load terminal conductor 11because of the engagement of the releasable member 24 with latch membe16 of the trip unit 15. I

If it is required to manually open the circuit, the handle 22 is shiftedto the left from the positionshown in FIG. 1. In this way, when the axisof tension spring 28 passes across the center line of the straightenedtoggles 25 and 26, the collapsible linkage including toggle links 25 and26 and releasable member 24, is collapsed, as shown in FIG. 2, to causethe movable contact arm 19 to rotate counterclockwise to therebyrespectively separate the movable contacts 20 and 21 from the stationarycontacts 13 and 14. It is noted, however, when this occurs, that the oneend 'of the releasable. member 24 remains engaged with the latch member16 of trip unit 15.

The releasable member 24 carries on its rightwardly disposed side, asviewed in FIG. 1, a swingable wedge member 29 being pivoted thereon by apin member 30. A cooperating stationary pin member 31 is supported on anupstanding leg member 32 which is mounted in the casing 10. I

As is well known, an arc chute generally indicated by the referencenumeral 33 is mounted in the casing 10 so as to surround the arcingcontacts 14 and 21. The chute includes a pair of side walls 34, only onebeing shown, made of. an insulating material, and a plurality of stackedarc-extinguishing metal plates 35, each having a V-shaped slot 36 forelongation of the electric arc to be initiated between the separatedarcing contacts 14 and 21.

When the manually operable handle 32 is positioned in the ON position toengage the movable contact 20 of movable contact arm 19 with thestationary contact 13 of load terminal conductor 11, the electriccircuit made may be traced from line terminal conductor 12 throughconductor 18, movable contact arm 19, movable contact 20 and stationarycontact 13 to load terminal conductor 11. v

For convenience of illustration, the molded case circuit breaker of FIG.1 has been shown as having only one trip unit 15. Actually, a trip unit15 is, however, provided for each pole or phase of the 'poli-phasecircuit breaker, and the thermally actuated and electromagneticallyoperated trip mechanism mounted in each trip unit are responsive to anexcessive current condition existing in each pole or phase to cause thecommon latch member 16 to release the hook extension of releasablemember 24 through a rotatable trip bar, not shown, extending through therespective trip units 15 when an excessive current condition occurs inat least one of the poles or phase conductors of the circuit breaker.

When the extension portion of releasable member 24 becomes free from thelatch member 16, the tension spring 28 will lift the toggle knee 27 oftoggle links'25 and 26 rapidly upward, being accompanied by the pivotalmovement of the movable contact arm 19 as well as the releasable member24. Thus, the movable main contact 20 can be separated in a no-arc statefrom the stationary main contact 13 because the separation of themovable arcing contact 21 from the stationary arcing contact 14 isbehind the main contact separation.

' The electric are initiated between the separated arcing contacts 14and 21 is elongated in the slots 36 of the stacked metal plates 35 to bedivided into a plurality of shortened arcs by the stacked metal plates,and then is extinguished.

During the separation movement of the movable contact arm 19, theswingable wedge member 29 will be lifted up through the releasablemember 24'by the spring 28. In this way, the swingable wedge member 29will slide in between one side of the toggle link 25 and thestationarypin 31. The final stage of this movement is shown in FIG. 3, where thetoggle link 25 is shown being supported by the stationary pin 31 throughthe wedge member 29 in a fixed position which in turn maintains themovable contact arm ,19 at its highest level, or at its most separatedposition above-the stationary contacts 13 and 14.

From the above, in accordance with the present invention, it can beunderstood that the largest open-pole distance between the stationaryand movable contact's when an automatic trip occurs can be assured byonly one part, that is, the swingable wedge member 29 which slides inbetween the toggle link and the stationary pin 31 to prevent rebound ofthe movable contact arm 19 toward its initial circuit closed position.The molded case circuit breaker having a large interruption capacity canbe thus manufactured inexpensively by using less components than thoseof the prior art, and accordingly it becomes easier to assemble andmanufacture the breaker. Furthermore, since the wedge member 29 has aside which can slide smoothly along the side of toggle link 25, the samecan smoothly slide in between the toggle link 25 and the stationary pin'31 without any shock when an automatic trip occurs, and accordinglythere will be no mechanical fatigue of the toggle linkage or thecollapsible mechanism after repeated automatic trips.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by LettersPatent of theUnited States is:

l. A molded case circuit breaker comprising: a molded case made of aninsulating material; at least one stationary contact mounted in saidmolded case; at least one movable arm having a movable contact mountedthereon to be engageable with said stationary contact, said movable armbeing capable of movement between circuit closed and open positions; anautomatic trip unit having a latch member capable of movement to areleasable position in response to a predetermined overload condition ofsaid circuit;

I so.

a releasable member pivotally supported in said molded case and havingone end normally engageable with said latch member to maintainsaidmovable contact arm in said circuit closed position;

a pair of toggle links having substantially rectilinear side surfacesand pivotally engaged with each other at respective ends thereof, saidtoggle links having their other ends respectively pivoted to saidreleasable member and said movable contact arm;

a manually operable handle pivotally supported in said molded case andmovable between circuit closing and opening positions;

a tension spring stretchedbetween said manually operable handle and theinterconnecting point of the ends of said toggle links;

a stationary pin mounted in said molded case; and a wedge memberswingably mounted on said releasable member, said wedge member having apair of substantially rectilinear cam surfaces, the first of whichlinearly slides along a facing rectilinear said surface of one of saidtoggle links and the second of which linearly slides along saidstationary pin when an automatic trip of said releasable member iscaused by said latch member being moved to said releasable positionwhile said manually operable handle is positioned in the circuit closedposition.

member.

1. A molded case circuit breaker comprising: a molded case made of aninsulating material; at least one stationary contact mounted in saidmolded case; at least one movable arm having a movable contact mountedthereon to be engageable with said stationary contact, said movable armbeing capable oF movement between circuit closed and open positions; anautomatic trip unit having a latch member capable of movement to areleasable position in response to a predetermined overload condition ofsaid circuit; a releasable member pivotally supported in said moldedcase and having one end normally engageable with said latch member tomaintain said movable contact arm in said circuit closed position; apair of toggle links having substantially rectilinear side surfaces andpivotally engaged with each other at respective ends thereof, saidtoggle links having their other ends respectively pivoted to saidreleasable member and said movable contact arm; a manually operablehandle pivotally supported in said molded case and movable betweencircuit closing and opening positions; a tension spring stretchedbetween said manually operable handle and the interconnecting point ofthe ends of said toggle links; a stationary pin mounted in said moldedcase; and a wedge member swingably mounted on said releasable member,said wedge member having a pair of substantially rectilinear camsurfaces, the first of which linearly slides along a facing rectilinearsaid surface of one of said toggle links and the second of whichlinearly slides along said stationary pin when an automatic trip of saidreleasable member is caused by said latch member being moved to saidreleasable position while said manually operable handle is positioned inthe circuit closed position.
 2. The molded case circuit breakeraccording to claim 1, further comprising a vertical support memberrigidly mounted on said molded case, said stationary pin being affixedto said vertical support member substantially perpendicular thereto. 3.The molded case circuit breaker according to claim 1, wherein the pivotpoint of said wedge member on said releasable member is separate anddistinct from said pivot point of said toggle link on said releasablemember.